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From |
"William M. Doerner" <wmd07c@fsu.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: boxplot whiskers with -lv- versus -adjacent- |

Date |
Tue, 11 May 2010 10:43:35 -0400 |

Does anybody know what the -graph box- and -adjacent- commands are computing for their whiskers? They aren't using the typical +-1.5*IQR formula as listed in the help files and used by -lv-. The command -adjacent- adjusts the fence for min/max values, but the adjacent values are not lower=Q1-1.5*IQR and upper=Q3+1.5*IQR. The command -lv- computes the adjacent values with that formula, but it does not adjust the fence for min/max values. I am puzzled. I looked at the code, but I couldn't figure it out why the commands have different outputs. Here is what I was running: **BEGIN** use http://www.stata-press.com/data/r11/bplong, clear *graph box bp, over(when) over(sex) keep if sex==1 & when==2 summarize bp, detail local u=r(p75)+(3/2)*(r(p75)-r(p25)) local l=r(p25)-(3/2)*(r(p75)-r(p25)) local l=max(`l',r(min)) local u=min(`u',r(max)) di `u' di `l' adjacent bp lv bp graph box bp, ylabel(#50, angle(horizontal)) *Notice how the upper limit should be 173 instead of 169. **END** The difference between the commands is not as simple as "it's 5% and 95%." That looks true for the bp dataset, but it doesn't happen with the city temperature dataset. Here is more code to compare: **BEGIN** use http://www.stata-press.com/data/r11/bplong, clear local x "if sex==1 & when==2 & bp~=." summarize bp `x', detail adjacent bp `x' lv bp `x' sysuse citytemp.dta, clear summarize tempjuly, detail adjacent tempjuly lv tempjuly **END** Thanks in advance for any input! Will Doerner * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**st: RE: boxplot whiskers with -lv- versus -adjacent-***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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